Agricultural combines are large machines that harvest, thresh, separate and clean agricultural crops that bear grain. The clean grain obtained is stored in a grain tank arranged on the combine. The threshed straw is generally chopped and spread out on the field across the width of the chopping mechanism.
In one common arrangement, the cut crop material from which the grain is extracted is gathered by a laterally extending “header” that rests on a feederhouse which extends forward from the agricultural combine in the direction of travel of the combine as it travels through the field harvesting crop. The header extends transversely with respect to the direction of travel and can be as much as 40 or 50 feet wide. Typically, headers are supported on a feederhouse that has a width of 4-6 feet. The weight of the header holds it on the feederhouse.
The wider the headers are, the more sensitive they all are to forces that attempt to dislodge them from the feederhouse, such as impacts with the ground that may lift one end of the draper header up in the air.
Another problem that can dislodge a draper header from the feederhouse is a weight imbalance on one side of the feederhouse versus the other. In normal operation, this is not a serious problem. When the feederhouse is driven through a field, it harvests a swath of crop that falls on both sides of the header in equal volumes and weights. Upon occasion, however, it is anticipated that too much crop can accumulate on one side of the header, causing it to roll (i.e. rotate about a longitudinal axis extending in the direction of travel) until one end or the other contacts the ground, at which point there can be serious damage.
One particular scenario in which this can occur is when one side of the draper header becomes overloaded with crop as compared to the other side. This can happen, for example, when one of the endless belt conveyors that carry crop from the sides of the draper header into the middle begins to slip, or actually stops. If this happens, and a conveyor belt on one side of the draper header is stopped, the vehicle continues moving forward, and the reciprocating knife that extends in front of the now-stopped conveyor keeps operating to sever the crop plants from their roots.
Furthermore, the reel, which also continues operating, will push the now-cut crop plants rearward, continually adding them on top of the pile of cut crop material already piled up on the now-stopped conveyor belt.
If this cut crop material piles too deeply on the stopped conveyor belt, it can overbalance the draper header causing the draper header to tilt downward on the heavier laden side until it lifts off the feederhouse, rams into the ground, or both. This can cause serious damage to the draper header, and, even if it does not damage the draper header, can delay the farmer from harvesting as he must first manually unload the now-overburdened conveyor belt before he can attempt to started running again.
It is necessary that he first manually unload the conveyor belt, because any attempt to start the conveyor belt with a massive pile of cut crop material can cause the drive roller to slip with respect to the conveyor belt and burn the conveyor belt.
The problem may not be solved, however, merely by stopping the overloaded or slipping conveyor belt. For example if the left conveyor belt stops while it is loaded with crop, and crop continues to be conveyed by the right conveyor belt on the other side of the draper header 18 the crop arriving from the right conveyor belt jams against the stopped crop on the left conveyor belt where the two crop flows normally meet in the middle of the draper header. This jamming of a moving crop flow against a stationary, heavy layer of crop on the left conveyor prevents any crop on the right conveyor from entering the center conveyor and being carried away. As a result, the right conveyor belt continues moving, yet the crop disposed on top of the right conveyor belt piles up adjacent to the center conveyor, gradually building up on the right conveyor belt. Eventually this will overbalance the header due to the additional weight building up on the right conveyor belt. Alternatively, if the additional weight is too great, it will eventually stall the right conveyor belt, causing the right conveyor belt to slip. While the example in this paragraph speaks of the left conveyor belts stopping and the right conveyor belt continuing to move, the same is true in the opposite direction. When the right conveyor belt stops and the left conveyor belt continues to move, the same piling up of crop on the right conveyor belt can occur.
U.S. Pat. No. 5,855,108. is directed to an alarm monitor for belt slip in an agricultural combine. The belts are V-belts that transmit power between the engine and the rotor that threshes the crop. The control system compares ratios of rotor speed and engine speed to determine if slip occurs and generates an audible and a visible warning
U.S. Pat. No. 4,321,991 is directed to a torque responsive interrupt for an agricultural combine that monitors a pressure signal produced by hydraulic V-belt pulleys between the engine and the threshing mechanism and declutches the drive pulley when the oil pressure reaches a threshold.
U.S. Pat. No. 7,658,059 is directed to a reciprocating knife on an auger header that separately drives left and right side reciprocating knives (called “sickles”).
U.S. Pat. No. 7,669,393 is directed to a stall detection method for a lawnmower that detects a stall condition that uses a microprocessors-based controller to monitor engine speed and to declutch the rotating mower blades from the engine when the speed indicates an incipient stall condition.
The problem underlying the present invention is that of reducing or preventing the overloading of a conveyor belt on a draper header when that conveyor belt stops entirely or (alternatively) begins to slip under a too-heavy load and to prevent the overbalancing of the draper header due to crop accumulation (1) on the stalled/stopped/slipping belt or (2) on the other not-stalled/not-stopped/not-slipping belt.